1. Field of the Invention
This invention relates to a lift type latch device which, when used on a handleless hinged door, for example, normally keeps the door locked in a closed state and, when the door is to be released from the closed state, allows the door to open slightly in its opening direction after a light momentary push is given to the door.
2. Description of Prior Art
Japanese Utility Model Application Public Disclosure SHO No. 58(1983)-148160 discloses a lift type latch notable for the very small number of its component parts. More specifically, it consists of a total of only four component parts: a stationary cylinder, a rod, a cam rotatably fixed on the rod, and a coil spring adapted to be simultaneously contracted between the stationary cylinder and the rod during the closing of the door and allowed to accumulate therein the resilient force for expelling the rod from the stationary cylinder during the opening of the door. In this conventional device, the rod is provided on the leading end thereof with a forked clip serving to retain resiliently a strike fastened on the rear side of the door. When the door is in its closed state, therefore, this clip keeps firm hold of the strike on the door and prevents the door from randomly opening.
When the door is slightly pushed in and readied for being fully opened, after the rod has protruded from the stationary cylinder and the door has been allowed to open slightly, the person wishing to open the door pulls the door slightly toward himself with his hand and makes the strike come off the clip. During this period, the rod is required to be retained within the stationary cylinder against the force exerted by the hand in the direction of opening the door toward the person. When the door in an open state is to be closed, the strike is required to be retained in the clip at the leading end of the rod. When the person opens the door or closes it, therefore, he is required to use not merely the force for opening and closing the door but also an extra force for releasing the strike from the rod and returning the strike into retention in the rod. Consequently, the strike is required to bear a force for retaining the rod and, therefore, tends to break.